Disclosed herein are compositions related to light-curable resin based dental restorative materials that can provide self-etching and self-adhesive properties to a hard tooth structure. Conventional approaches to directly fill a dental cavity using esthetic, non-amalgam type material involve the utilization of glass-ionomer restoratives, resin-modified glass ionomers, compomers, or resin composite materials under different circumstances. The drawbacks of glass ionomers and resin-modified glass ionomers include high opacity (thus inferior esthetics), insufficient wear resistance, and insufficient fracture toughness, as compared to resin composites. The resin composite materials have improved mechanical properties, esthetic properties, and wear resistance, as compared to resin-modified glass ionomers and compomer materials. On the other hand, glass ionomer type materials can provide certain adhesive properties to a tooth structure, whereas resin-based composites require the use of a bonding agent prior the placement of a dental composite.
The utilization of a bonding agent prior to the placement of composite requires quite a number of procedures and can be highly technique-sensitive. After removing carious tooth structure and cleaning the cavity, the conventional total-etch adhesive procedures involve applying etching gel (normally 34%˜37% phosphoric etching gel) to acid-etching the tooth structure, rinsing with copious amount of water, air-drying, and if 4th generation adhesive is used, need to apply another layer of primer followed by solvent evaporation, before the bonding agent is applied. Certain dental bonding agents require the application of multiple layers of adhesive before solvent evaporation and light curing. The procedures for 5th generation bonding agents, such as Prime&Bond NT® and XP Bond® (available from DENTSPLY Caulk, Milford, Del.) are slightly simpler than 4th generation as the adhesive and primer are combined into one bottle and no separate priming step is required. Self-etch type adhesive can provide simpler procedures as there is no need for etching gel application and rinsing. Nevertheless, the overall utilization of bonding agents involves multi-step procedures and adequate isolation is needed to prevent contamination by saliva and/or blood during these steps.
Although traditional methods of etching the tooth structure by using a etchant, such as about 34% to about 37% phosphoric etching gel, are quite effective for removing the smear layer and improving the substrate's roughness for bonding, under certain circumstances such a procedure can also result in disrupted dentin surface through excessive etching on the sound dentin (over-demineralization) followed by collapsed dentinal collagen fibrils. Furthermore, depending upon the dental bonding agent being used, it might not penetrate to a depth of over-demineralized dentin, which can introduce post-operation sensitivity.
U.S. Pat. No. 6,660,785 describes the synthesis of self-adhesive polymerizable monomers and their application as a water containing and a water free self-adhesive dental/medical composite were described. The dental/medical composite comprises a self-adhesive polymerizable monomer, a polymerizable monomer, an acid reactive and/or reactive and/or non-reactive filler, a diluent, a polymerization initiator and a stabilizer. As polymerization initiators are used the commonly known thermal initiators, redox initiators and/or photo initiators. The new adhesive dental composite develops adhesion to dentine of about 4 MPa. Fillers of high X-ray absorbance provide radio-opacity values greater than that of the same thickness of aluminum.
US Patent Publication No. 2006/0004122 discloses a composition which is self-adhesive to the hard tooth tissue, comprising: (A) 5 to 75 percent by weight of one or more mono or higher functional ethylenically unsaturated compounds which additionally have an acid functional group, wherein one of said compounds has a P—OH group, for instance a phosphoric, phosphonic or phosphinic acid group; (B) 2 to 50 percent by weight of one or more mono or higher functional ethylenically unsaturated compounds without any acid functional group; (C) 22.8 to 85 percent by weight of filling material(s), comprising at least one filling material that may react with component (A) in the sense of causing a ion exchange, neutralization, salt formation and/or chelate formation reaction; (D) 0.1 to 8 percent by weight of one or more initiators and optionally activators; (E) 0.1 to 20 percent by weight of further additives, for example, modifiers, wherein the weight ration in % of component (A) relative to component (B) ranges from 21 to 90:10 to 79.
US Patent Publication No. 2007/0197683 discloses a self-etching and self-adhesive dental composition, comprising a polymerizable (meth)acrylate carboxylic acid/anhydride; a copolymerizable multi-functional (meth)acrylate resin; a copolymerizable diluent monomer; and a curing system. The composition has the advantage of not requiring a separate etching and bonding step.
US Patent Publication No. 2010/0041786 discloses a dental restorative composition comprising (A) polymerizable monomer(s) having at least one phosphorus-containing acidic moiety and at least one ethylenically unsaturated group; (B) polymerizable monomer(s) having a molecular weight of 100-250, at least one hydroxyl group, and at least one ethylenically unsaturated group; (C) polymerizable monomer(s) having a molecular weight of 270-900, at least two ethylenically unsaturated groups and no acidic functional group; (D) photo-initiator(s); and (E) filler(s) each having a mean particle size of more than 0.005 microns and less than 70 microns. The weight ratio of (A+B):(C) ranges from 30:70 to 90:10, the concentration of (A) is 10-50 wt. %, the concentration of (B) is 15-60 wt. %, and the composition has a shear bond strength of at least 10 MPa to both dentin and enamel. Also provided is a method for filling a dental cavity with the composition without first treating the dental cavity with an etchant, a primer and/or an adhesive.
It is therefore quite desirable to have a single-component tooth filling material, such as polymerizable dental restorative composite, to bond to the tooth structure surrounding the cavity after treating the tooth surface with primer. It is further desirable to have a single-part, shelf-stable composition that can provide self-etching and self-adhesion to untreated tooth substrate. A self-adhesive composite that can provide adequate self-etching, self-priming, and self-adhesion to tooth, while not compromising other key properties obtainable from conventional composites is hence quite advantageous. Such dental restorative compositions can provide tremendous reduction in both placement time and technique-sensitivity, when compared with the use of bonding agent that may involve separate etching, rinsing, drying, priming, before the final adhesive placement and curing step.